How do I change where imported objects appear in the world?
Objects appear in the center of the world because that is where the 3D cursor is set by default. 

All objects have what is called an origin (a pivot point or a "center", usually represented by an orange dot) The origin of the the created object is then placed where the 3D cursor is on the scene. 



But you can move the 3D cursor wherever you want the new objects to appear. Note that the origin of the new object will be at the 3D cursor's position.



To have your objects appear in a different place, just move the 3D cursor.